Avionic communication devices are well known in the field of aviation electronic (avionic) instruments. The method and apparatus of communication between communication devices implemented by known prior art systems depends on the capabilities of system resources, such as communications paths between the devices. As increased system capability also generally increases system cost, the method of communication implemented by communication devices is a function of overall system cost.
One feature of increased system capability cost involves the communication of audio information between a communication panel and a radio. One example of a radio is a very-high frequency (VHF) receiver/transmitter.
Airplane cockpits have high levels of noise. The noise interferes with, and reduces, the effectiveness of audio communications in the cockpit. Headsets are often used to counteract high levels of noise in an airplane cockpit. Audio communication includes conversation between members of the flight crew, listening to radio flight communications, and speaking into microphones for radio flight transmissions. Often, at least one member of the flight crew wears a headset that includes headphones and microphones for audio communication. The headset is operably coupled to a communication panel. The communication panel is mounted on a cockpit instrument panel in the cockpit. The communication panel is operably coupled to a radio through an entirely analog communication path. The radio allows communication with ground stations and other aircraft.
Electromagnetic disturbances often interfere with analog radio communication. The communication of audio information between the radio and the communication panel is analog. Furthermore, the communication of audio information between the communication panel and the headset is analog. Analog communication is interfered by external electromagnetic disturbances. Electromagnetic disturbances are caused by a number of sources, such as ignition in an airplane engine, and the operation of an electromechanical device in the airplane, such as a servo, an air-conditioner compressor, or an autopilot device. To make matters worse, these sources are typically located within a few feet of the analog communication path, which increases the strength of the electromagnetic disturbance in the analog communication path. The communication path is typically comprised of two lines, one line for each direction of communication.
Furthermore, the extent or degree of electromagnetic disturbance in the analog line between the radio and the communication panel is in the order of 14 or even 28 volts. In contrast, the electrical potential in the electromechanical devices is 0.50 volts. Thus, the magnitude of the electrical disturbance of the electro-mechanical devices and the analog line can therefore be up to 56 times the voltage in the analog line. This high magnitude can overwhelm an analog signal in the analog line.
In order to reduce the electromagnetic interference, expensive wiring is implemented as the analog communication lines. Conventionally, a twisted shield pair is implemented as the analog communication lines, in which two lines are combined into one line. The twisted shielded wiring typically costs between $50 and $100 for each line, yielding a total cost for the two lines of at least $100, if not $200.
In summary, conventional avionic systems communicate analog audio signals between a communication panel and a radio through two relatively costly twisted shielded cables. Therefore, there exists a need for systems, methods, and apparatus adapted to communicate audio signals between a communication panel and radio through less expensive cabling that provides protection from electromagnetic disturbances.